Digital-to-analog converter (DAC) circuits are well known in the integrated circuit art. These are circuits that convert a digital word comprising N bits to an equivalent analog signal, typically either voltage or current. One of the most common approaches to implementing a linear DAC on an integrated circuit is what is known as a “current-mode DAC”. In this case, the output current is produced by a plurality of binary weighted current sources connected to respective switches whose outputs are, in turn, connected to the common analog output.
Typically, the switches are implemented using CMOS pass gates or CMOS (or bipolar) differential pairs. Since the actual DAC output current flows through the switches, the switches must be sized properly to avoid introducing non-linearity into the DAC transfer function. Most typically, these switch sizes are also binary weighted, each one matching the current mirror group to which it is connected. These switches lead to increased area and reduced performance in the DAC.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.